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    Degree of sulfate-reducing activities on COD removal in various reactor configurations in anaerobic glucose and acetate-fed reactors
    (WILEY, 2007) Erdirencelebi, Dilek; Ozturk, Izzet; Cokgor, Emine Ubay; Tonuk, Gulseren Ubay
    Sulfate-reduction data from various anaerobic reactor configurations, e.g., upflow anaerobic sludge blanket reactor (UASBR), completely stirred tank reactor (CSTR), and batch reactor (BR) with synthetic wastewaters, having glucose and acetate as the substrates and different levels of sulfate, were evaluated to determine the level of sulfate-reducing activity by sulfate-reducing bacteria coupled to organic matter removal. Anaerobic reactors were observed for the degree of competition between sulfate-reducing sulfidogens and methane producing bacteria during the degradation of glucose and acetate. Low sulfate-reducing activity was obtained with a maximum of 20% of organic matter degradation with glucose-fed upflow anaerobic sludge bed reactors (UASBRs), while a minimum of 2% was observed with acetate-fed batch reactors. The highest sulfate removal performance (72-89%) was obtained from glucose fed-UASB reactors, with the best results observed with increasing COD/SO4 ratios. UASB reactors produced the highest level of sulfidogenic activity, with the highest sulfate removal and without a performance loss. Hence, this was shown to be the optimum reactor configuration. Dissolved sulfide produced as a result of sulfate reduction reached 325 mg/L and 390 mg/L in CST and UASB reactors, respectively, and these levels were tolerated. The sulfate removal rate was higher at lower COD/SO4 ratios, but the degree of sulfate removal improved with increasing COD/SO4 ratios.
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    Effects of 4-Chloro-Aliphatic Hydrocarbons on Microbial Activities of Anaerobic Landfill Leachate Digestion
    (SCIENCE PRESS BEIJING, 2009) Erdirencelebi, Dilek; Ozturk, Izzet
    Three four-chloro-aliphatic hydrocarbons (carbon tetrachloride (CT), tetrachloroethylene (PCE) and 1, 1, 2, 2-tetrachloroethane (1, 1, 2, 2-PCA)) were spiked individually at concentrations from 0.145 mg/L to 2.4 mg/L to anaerobic batch reactors treating young landfill leachate undergoing competition between main microbial groups of anaerobic consortia for an experimental period of four months. The effect of chlorinated compounds on the reactors' organic matter removal performance and microbial activities was examined. Dissolved organic matter was removed at similar rates in all reactors. Gas production ceased in CT receiving reactors and decreased in PCE receiving reactors revealing inhibition on methanogens with no effect in PCA receiving reactors. Sulfate-reducing bacteria's activity was less inhibited by chlorinated aliphatic compounds than methanogenic activity. Chlorinated aliphatic hydrocarbons (CAHs) were monitored and biotransformation of PCE and PCA to TCE and 1, 1, 2-TCA was observed via reductive dechlorination and dehydrohalogenation.
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    Organic Matter Removal Kinetics and Sulfide Inhibition Pattern of Young Landfill Leachate Treatment
    (SCIENCE PRESS BEIJING, 2009) Erdirencelebi, Dilek; Ozturk, Izzet
    Young landfill leachate digestion was monitored for soluble organic matter removal and sulfide production in anaerobic batch reactors. COD removal kinetics and inborn sulfide inhibition pattern were determined according to extended Monod kinetics for product inhibition. The inhibition pattern suited noncompetitive inhibition model with a critical inhibitor concentration (K(i)) of 850 mg S(2-)/L. Kinetic constants k and K(s) were determined accordingly. Organic matter removal followed a second order reaction kinetics. The maximum dissolved sulfide production obtained was 450 mg S(2-)/L and COD removal proceeded at a range of 81-93% with a minimum level of 67-76% as a result of a drop in pH intensifying H(2)S toxicity. Organic loading rate was applied at values from 0.18 kg COD/m(3).d to 0.5 kg COD/m(3).d where increasing rates enhanced methanogenic activity and sulfide production was stabilized at a level of 100-130 mg S(2-)/L accordingly. Results showed that methanogenic activity ameliorated at higher OLRs indicating that they were also subject to competition for substrate as well as sulfide inhibition despite a high COD/SO(4) ratio.
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    System performance in UASB reactors receiving increasing levels of sulfate
    (WILEY, 2007) Erdirencelebi, Dilek; Ozturk, Izzet; Cokgor, Emine Ubay
    Glucose-fed high-rate UASB reactors were tested at three COD/SO4 ratios and hydraulic retention times to promote sulfate reducing activity and observe the effects on reactor performance. Different COD/SO4 ratios (20, 10, and 5) resulted in changes in organic matter removal, methane production, alkalinity, dissolved sulfide and biomass concentrations and profile. The COD removal dropped from 95 to 80-84% at the lowest COD/SO4 ratio. Sulfate was removed at 79 to 89% at the highest ratio and dropped to 72 to 74% with increasing sulfate loading. Alkalinity was produced at higher levels with increasing sulfate loading. Specific methane production dropped with decreasing hydraulic retention times. Sulfate-reducing activity used a maximum of 11.7% of organic matter at the highest sulfate loading level, producing a slight shift to sulfate-reducing activity in the substrate competition between sulfate-reducing bacteria and methanogens. Increased sulfate loading at COD/SO4 ratios of 10 and 5 caused deterioration of the concentration profile of the sludge, resulting in biomass washout and decreased volatile fraction of biosolids in the reactors.